For some years, we have been using the unique tool of inbred guinea pigs available at the NIH for investigation of particular areas of the immune response concerned with mechanisms of hypersensitivity and protection against infectious and autoimmune diseases. Advantages lie in the ability to perform viable adoptive transfers of lymphoid cells and in the capacity to study genetic factors in certain hypersensitivity and autoimmune phenomena. For these reasons, we have concentrated recently on the pathogenesis of an age-dependent, strain-dependent chronic autoimmune encephalomyelitis which is strongly reminiscent of multiple sclerosis in man, and on the prevention and treatment of this condition using various tolerance-inducing techniques. BIBLIOGRAPHIC REFERENCES: Raine, C.S., Snyder, D.H., Stone, S.H. and Bornstein, M.B.: Suppression of acute and chronic experimental allergic encephalomyelitis in strain 13 guinea pigs. J. Neurol. Sci., 355-367, 1977. Snyder, D.H., Stone, S.H. and Raine, C.S.: Attempts to induce chronic experimental allergic neuritis in strain 13 and Hartley guinea pigs. J. Neuropath. Exp. Neurol. 36: 488-498, 1977.